This invention relates to low drift spray nozzles and a method of spraying and, more particularly to spray nozzles and a method of spraying in which a flat spray is produced having large droplets of liquid therein.
The production of sprays having substantially large droplets and low drift characteristics has become increasingly important in recent years. By way of example, one application in which drift must be minimized is in the application of herbicides, pesticides and other farm chemicals. Indeed, Federal, as well as local agencies have frequently arbitrarily set limits on the amount of drift which is permissible in the application of certain chemicals and other materials.
Several approaches have been taken in the past in an attempt to minimize spray drift.
One such approach utilizes flooding or deflector type nozzles which are generally operated at very low pressures, frequently as low as 3 or 4 psig. These low pressures result in the generation of large droplets which reduce the possibility of drift hazards. However, the low pressures in such flooding or deflector type nozzles produce several important disadvantages, including difficulty in obtaining a good spray patternation and coverage uniformity. In addition, any variation in the supply pressure or pressure losses in the equipment itself inherent in the piping will cause a change of flow rate through the nozzles and adversely affect uniformity of coverage.
Another approach to reduce drift has been to foam the liquid being sprayed. U.S. patent to Sherman E. Conrad and Dennis W. Bintner, U.S. Pat. No. 3,836,076, discloses a nozzle useful in such foaming techniques. Such foaming techniques, likewise, suffer several disadvantages. One disadvantage is that a particular foam generating liquid must be utilized at the application site to produce the foamed discharge. Such liquid not only constitutes an added expense, but also necessitates the provision of extra equipment, such as extra tanks and metering equipment. In addition such foam generating nozzles and equipment are relatively bulky and require the introduction of air into the foam generating nozzle. Moreover, the nozzle shown in the last mentioned Letters Patent includes a plurality of small jetting nozzles which may be subject to plugging from contaminants.
In U.S. patent to Kenneth E. Reed, U.S. Pat. No. 3,934,823, a low drift spray nozzle and method are disclosed for producing a hollow conical spray cone composed primarily of large droplets of liquid to reduce drift. In that nozzle and method, a swirling motion is first imparted to the liquid and then this swirling liquid is passed through several orifices to form the swirling hollow conical discharge containing the large droplets of the liquid. The nozzle and method disclosed in the last mentioned patent ovecome many of the disadvantages inherent in the use of flooding or deflector type nozzles and the foam systems.
The present invention is an improvement over the nozzle and method disclosed in U.S. Pat. No. 3,934,823 in that the nozzle and method of the present invention are capable of producing a flat spray pattern having large droplets of liquid therein, rather than the large droplet, hollow conical pattern disclosed in the last mentioned patent. In the nozzle and method incorporating the principles of the present invention, liquid pressures greatly in excess of those employed with the prior flooding or deflector type nozzles may be utilized and yet the generation of large droplets which are not subject to drift is optimized. Accordingly, since the method and nozzles of the present invention are capable of operating under substantially higher line pressures, the adverse effect of changes in elevation, frictional losses and the like attending the use of the flooding or deflector type nozzles are minimized. The nozzles and method incorporating the principles of the present invention result in excellent patternation definition and uniform distribution of droplet sizes and droplet quality is not substantially altered by changes in size or capacity of the nozzles. The nozzles and method of the present invention also result in a large droplet, low drift spray without necessitating the addition of foaming agents, air or other gases to the spray and thereby avoid the disadvantages inherent in the use of such additional fluids. Finally, the nozzles and method incorporating the principles of the present invention are simple and compact in manufacture, construction and operation, and are not subject to plugging from contaminants.
In a principal aspect of the present invention, a nozzle for producing a flat spray discharge having substantially large droplets of liquid therein, includes a substantially gas free turbulence chamber, first orifice means for introducing a jet of liquid into the turbulence chamber, a second chamber, partition means between the turbulence chamber and the second chamber having a surface positioned in the path of the jet such that the jet of liquid impinges on the surface to cause turbulence in the turbulence chamber, passage means for conducting the turbulent liquid past the partition means from the turbulence chamber to the second chamber, and discharge orifice means at the end of the second chamber for discharging the turbulent liquid from the second chamber in the form of the flat spray pattern having large liquid droplets therein.
In another principal aspect of the present invention, a method of producing large droplets of liquid includes producing a jet of the liquid, directing the jet of liquid against an impingement surface to produce a substantially gas free zone of turbulence adjacent the upstream side of the impingement surface, flowing the turbulent liquid from the zone of turbulence past the impingement surface to a chamber, and discharging the turbulent liquid from the chamber through a discharge orifice.